For a wide variety of industrial textile wet treatment processes--such as washing, bleaching, scouring, mercerization, dyeing, and desizing--apparatus commonly referred to as a horizontal washer has proven to be very practical and effective. Such apparatus, which is generally described in U.S. Pat. No. 4,095,442 and German Off. 2,521,600, includes a chamber through which the web passes in serpentine fashion along substantially horizontal, vertically spaced, travel paths. The web is supported by a plurality of rollers rotatable about horizontal axes and disposed in two vertical columns, the rollers in each column being horizontally spaced from the rollers in the other column and vertically offset with respect thereto. An entry for the web is provided at the lower portion on one side of the chamber, and an exit for the web is provided on the opposite side of the chamber, usually at the bottom or top. Means are provided for introducing treating liquid (e.g., wash or rinse water) at the top of the chamber to pass downwardly in the chamber to treat the web at various horizontal travel paths. A drain tank is also provided at the bottom of the chamber, occupying substantially the entire bottom thereof.
While such apparatus is eminently suited for the continuous wet treatment of moving webs, oftentimes the effective treatment capacity of a chamber is reduced as a result of the inability of the treatment liquid to pass properly from one web level to the next, the lower web travel paths sometimes remaining untreated, the web receiving treatment until it passes to the upper travel path closer to the treatment liquid introducing structure. Such reduction in treatment capacity is especially characteristic of heavy, tight fabric constructions (densely beaten woven fabrics). One suggested approach for minimizing this problem is provided in U.S. Pat. No. 4,092,839 wherein a plurality of accessory roller systems are provided mounted at one side of the chamber, with immersion pans associated with such roller systems, and with the treatment liquid introducing structure oriented to spill onto that side of the chamber. In this structure, an accessory liquid seal is provided at the bottom of the chamber at the web exit.
Another problem sometimes encountered with conventional horizontal washers is a low turnover rate of treatment liquid, and greater than desired steam consumption, due in part to the large volume of the drain tank provided at the bottom of the chamber, relatively large liquid volumes in the liquid seals, and due to the sewering of the spent treatment liquid from the last of any series of treatment chambers.
According to the present invention, the above-mentioned drawbacks associated with conventional horizontal washers have been eliminated. The problem of reduced treatment capacity is overcome by providing means for introducing treating liquid into the chamber at an intermediate portion of the chamber vertically between the top liquid introducing structure and the web entry. Preferably such intermediate treatment liquid introducing structure comprises a liquid seal forming the web exit. A trough disposed adjacent the top of the liquid seal may extend into the chamber and direct overflow from the liquid seal onto the web at a horizontal travel path thereof, and another trough may extend out from the chamber to a point under a pair of squeezing rollers for directing liquid squeezed out of the web by the squeezing rollers to the liquid seal. Such an arrangement provides a minimum amount of additional structure compared to prior art arrangements, yet results in the desired flow effective treatment capacity of the washer.
The problem of low treatment liquid turnover rate and high steam consumption is solved, according to the present invention, by providing the entry and exit liquid seals of low volume, and by providing the drain tank of much less volume, the drain tank taking up only about one-half of the bottom area of the chamber, on the side thereof at which the web exit is provided. Additionally, the chambers can be provided in series, and the spent treatment liquid from the first chamber of the series can be passed through a heat exchanger with fresh treatment liquid for the last chamber of the series to thereby preheat the fresh treatment liquid, and minimize steam consumption.
Additionally, according to the present invention by the proper interconnection of treatment chambers (either in a recirculation system or a counterflow system), liquid is introduced at a point where the degree of contamination (or how spent the liquid is) matches the liquid in the counterflow, so that as the liquid moves from the last to the first treatment chamber it becomes progressively more contaminated (or expends more of its chemical treating capacity).
It is the primary object of the present invention to provide an improved horizontal washer. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.